Lecture 2
Earth System Science
All physical, chemical, and biological components (give examples) of the Earth are inter-twinned and therefore must be studied simultaneously to be understood from a process-oriented point of view
Life history, therefore, is best understood in the context of a changing and evolving Earth System.
The geologic record provides an important and singularly unique insight into how evolution and extinction events and cycles take place on our planet.
Biocomplexity
The study of complexity arising from the interplay of biological, physical, and chemical systems across multiple spatial (microns to thousands of kilometers) and temporal (nanoseconds to eons) scales. Research on the individual components of complex systems provides only limited information about the behavior of these systems as a whole.
Key Unifying Themes
1. The Earth is a unique evolving system requiring an earth System Science approach
2. Plate Tectonics (Harry Hess, 1960's) is a unifying theme that
explains and provides a dynamic context for earth system processes
(Fig. P-6). Made up of core, mantle, crust concentric layers (Fig.
1.19). Crust composed of large discrete pieces, called plates.
Mantle convection the driving force (Fig. 1.18)
3. The Earth is very old ~ 4.6 billion, and thus the present and
future earth system is the product of a long and complex history
4. Internal and external earth processes interact at the earth's
surface, which influence life. Physical environments have influenced
the development of life, and life in turn has emerged to influence
the development of the Earth's physical environments
Conceptual Approaches -
Uniformatarianism (James Hutton, Charles Lyell) actualism - "the present is the key to the past" a long gradual Earth history (give examples)
Catastrophism (Abraham Werner, Charles Cuvier) Earth history is punctuated by sudden large episodic events that control overall development of geology and life on Earth (give examples)
Reality is that both types of processes have and do occur
Types of Rocks
Igneous crystalline rock formed from the cooling of molten rocks (intrusive magma, extrusive volcanics)
Sedimentary rocks formed from grains created by the erosion of prexisting rocks, biotic skeletons, or chemical precipitates.
Tied closely to the Water Cycle (Fig. 1.21)
Stratification and bedding
Nicolaus Steno's Three Laws for Sedimentary Rocks
1. Principle of Superposition
2. Principle of Original Horizontality
3. Principle of Lateral Continuity
Metamorphic crystalline rock formed by the physical and
chemical alteration of
pre-exisitng rocks under elevated temperatures and pressures (Fig.
1.7)
Global Dating and Geologic Time
Relative Age Dating
fossils and their stratigraphic distribution, fossil succession (consistent and predictable appearance and disappearence through time, William "Strata" Smith)
event markers Ir anomalies, volcanic ash beds, oceanic anoxic events
Absolute Age Dating
Radioactive decay of naturally occurring elements and their isotopes
Layers (lake sediments) and rings (trees)
The Geologic Time Scale Fig. 1.13 p. 13, Fig.
The oldest rocks are ~ 3.8 billion years old